Chloroplast pentose-5-phosphate 3-epimerase from potato: cloning, cDNA sequence, and tissue-specific enzyme accumulation.

A cDNA clone encoding the chloroplast enzyme pentose-5-phosphate 3-epimerase (EC 5.1.3.1) in potato (Solanum tuberosum) was isolated and sequenced. The deduced sequence of 235 amino acids is similar to protein sequences of bacterial epimerases. Northern blot analysis showed the highest level of epimerase mRNA expression in potato leaves, whereas it was low in roots, tubers, and stems. Epimerase protein is mulated only in plant tissues possessing chloroplasts, i.e. in land to a lesser extent in stem. In contrast, transketolase, a sequential enzyme of epimerase in the reductive and oxidative pentose phosphate cycle, is accumulated in all plant tissues.